/*
 * Copyright (c) 2003, 2015, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package javax.sql.rowset.serial;

import java.sql.*;
import java.io.*;
import java.lang.reflect.*;
import java.util.Arrays;


/**
 * A serialized mapping in the Java programming language of an SQL
 * <code>BLOB</code> value.
 * <P>
 * The <code>SerialBlob</code> class provides a constructor for creating
 * an instance from a <code>Blob</code> object.  Note that the
 * <code>Blob</code>
 * object should have brought the SQL <code>BLOB</code> value's data over
 * to the client before a <code>SerialBlob</code> object
 * is constructed from it.  The data of an SQL <code>BLOB</code> value can
 * be materialized on the client as an array of bytes (using the method
 * <code>Blob.getBytes</code>) or as a stream of uninterpreted bytes
 * (using the method <code>Blob.getBinaryStream</code>).
 * <P>
 * <code>SerialBlob</code> methods make it possible to make a copy of a
 * <code>SerialBlob</code> object as an array of bytes or as a stream.
 * They also make it possible to locate a given pattern of bytes or a
 * <code>Blob</code> object within a <code>SerialBlob</code> object
 * and to update or truncate a <code>Blob</code> object.
 *
 * <h3> Thread safety </h3>
 *
 * <p> A SerialBlob is not safe for use by multiple concurrent threads.  If a
 * SerialBlob is to be used by more than one thread then access to the SerialBlob
 * should be controlled by appropriate synchronization.
 *
 * @author Jonathan Bruce
 */
public class SerialBlob implements Blob, Serializable, Cloneable {

  /**
   * A serialized array of uninterpreted bytes representing the
   * value of this <code>SerialBlob</code> object.
   *
   * @serial
   */
  private byte[] buf;

  /**
   * The internal representation of the <code>Blob</code> object on which this
   * <code>SerialBlob</code> object is based.
   */
  private Blob blob;

  /**
   * The number of bytes in this <code>SerialBlob</code> object's
   * array of bytes.
   *
   * @serial
   */
  private long len;

  /**
   * The original number of bytes in this <code>SerialBlob</code> object's
   * array of bytes when it was first established.
   *
   * @serial
   */
  private long origLen;

  /**
   * Constructs a <code>SerialBlob</code> object that is a serialized version of
   * the given <code>byte</code> array.
   * <p>
   * The new <code>SerialBlob</code> object is initialized with the data from the
   * <code>byte</code> array, thus allowing disconnected <code>RowSet</code>
   * objects to establish serialized <code>Blob</code> objects without
   * touching the data source.
   *
   * @param b the <code>byte</code> array containing the data for the <code>Blob</code> object to be
   * serialized
   * @throws SerialException if an error occurs during serialization
   * @throws SQLException if a SQL errors occurs
   */
  public SerialBlob(byte[] b)
      throws SerialException, SQLException {

    len = b.length;
    buf = new byte[(int) len];
    for (int i = 0; i < len; i++) {
      buf[i] = b[i];
    }
    origLen = len;
  }


  /**
   * Constructs a <code>SerialBlob</code> object that is a serialized
   * version of the given <code>Blob</code> object.
   * <P>
   * The new <code>SerialBlob</code> object is initialized with the
   * data from the <code>Blob</code> object; therefore, the
   * <code>Blob</code> object should have previously brought the
   * SQL <code>BLOB</code> value's data over to the client from
   * the database. Otherwise, the new <code>SerialBlob</code> object
   * will contain no data.
   *
   * @param blob the <code>Blob</code> object from which this <code>SerialBlob</code> object is to
   * be constructed; cannot be null.
   * @throws SerialException if an error occurs during serialization
   * @throws SQLException if the <code>Blob</code> passed to this to this constructor is a
   * <code>null</code>.
   * @see java.sql.Blob
   */
  public SerialBlob(Blob blob)
      throws SerialException, SQLException {

    if (blob == null) {
      throw new SQLException(
          "Cannot instantiate a SerialBlob object with a null Blob object");
    }

    len = blob.length();
    buf = blob.getBytes(1, (int) len);
    this.blob = blob;
    origLen = len;
  }

  /**
   * Copies the specified number of bytes, starting at the given
   * position, from this <code>SerialBlob</code> object to
   * another array of bytes.
   * <P>
   * Note that if the given number of bytes to be copied is larger than
   * the length of this <code>SerialBlob</code> object's array of
   * bytes, the given number will be shortened to the array's length.
   *
   * @param pos the ordinal position of the first byte in this <code>SerialBlob</code> object to be
   * copied; numbering starts at <code>1</code>; must not be less than <code>1</code> and must be
   * less than or equal to the length of this <code>SerialBlob</code> object
   * @param length the number of bytes to be copied
   * @return an array of bytes that is a copy of a region of this <code>SerialBlob</code> object,
   * starting at the given position and containing the given number of consecutive bytes
   * @throws SerialException if the given starting position is out of bounds; if {@code free} had
   * previously been called on this object
   */
  public byte[] getBytes(long pos, int length) throws SerialException {
    isValid();
    if (length > len) {
      length = (int) len;
    }

    if (pos < 1 || len - pos < 0) {
      throw new SerialException("Invalid arguments: position cannot be "
          + "less than 1 or greater than the length of the SerialBlob");
    }

    pos--; // correct pos to array index

    byte[] b = new byte[length];

    for (int i = 0; i < length; i++) {
      b[i] = this.buf[(int) pos];
      pos++;
    }
    return b;
  }

  /**
   * Retrieves the number of bytes in this <code>SerialBlob</code>
   * object's array of bytes.
   *
   * @return a <code>long</code> indicating the length in bytes of this <code>SerialBlob</code>
   * object's array of bytes
   * @throws SerialException if an error occurs; if {@code free} had previously been called on this
   * object
   */
  public long length() throws SerialException {
    isValid();
    return len;
  }

  /**
   * Returns this <code>SerialBlob</code> object as an input stream.
   * Unlike the related method, <code>setBinaryStream</code>,
   * a stream is produced regardless of whether the <code>SerialBlob</code>
   * was created with a <code>Blob</code> object or a <code>byte</code> array.
   *
   * @return a <code>java.io.InputStream</code> object that contains this <code>SerialBlob</code>
   * object's array of bytes
   * @throws SerialException if an error occurs; if {@code free} had previously been called on this
   * object
   * @see #setBinaryStream
   */
  public java.io.InputStream getBinaryStream() throws SerialException {
    isValid();
    InputStream stream = new ByteArrayInputStream(buf);
    return stream;
  }

  /**
   * Returns the position in this <code>SerialBlob</code> object where
   * the given pattern of bytes begins, starting the search at the
   * specified position.
   *
   * @param pattern the pattern of bytes for which to search
   * @param start the position of the byte in this <code>SerialBlob</code> object from which to
   * begin the search; the first position is <code>1</code>; must not be less than <code>1</code>
   * nor greater than the length of this <code>SerialBlob</code> object
   * @return the position in this <code>SerialBlob</code> object where the given pattern begins,
   * starting at the specified position; <code>-1</code> if the pattern is not found or the given
   * starting position is out of bounds; position numbering for the return value starts at
   * <code>1</code>
   * @throws SerialException if an error occurs when serializing the blob; if {@code free} had
   * previously been called on this object
   * @throws SQLException if there is an error accessing the <code>BLOB</code> value from the
   * database
   */
  public long position(byte[] pattern, long start)
      throws SerialException, SQLException {

    isValid();
    if (start < 1 || start > len) {
      return -1;
    }

    int pos = (int) start - 1; // internally Blobs are stored as arrays.
    int i = 0;
    long patlen = pattern.length;

    while (pos < len) {
      if (pattern[i] == buf[pos]) {
        if (i + 1 == patlen) {
          return (pos + 1) - (patlen - 1);
        }
        i++;
        pos++; // increment pos, and i
      } else if (pattern[i] != buf[pos]) {
        pos++; // increment pos only
      }
    }
    return -1; // not found
  }

  /**
   * Returns the position in this <code>SerialBlob</code> object where
   * the given <code>Blob</code> object begins, starting the search at the
   * specified position.
   *
   * @param pattern the <code>Blob</code> object for which to search;
   * @param start the position of the byte in this <code>SerialBlob</code> object from which to
   * begin the search; the first position is <code>1</code>; must not be less than <code>1</code>
   * nor greater than the length of this <code>SerialBlob</code> object
   * @return the position in this <code>SerialBlob</code> object where the given <code>Blob</code>
   * object begins, starting at the specified position; <code>-1</code> if the pattern is not found
   * or the given starting position is out of bounds; position numbering for the return value starts
   * at <code>1</code>
   * @throws SerialException if an error occurs when serializing the blob; if {@code free} had
   * previously been called on this object
   * @throws SQLException if there is an error accessing the <code>BLOB</code> value from the
   * database
   */
  public long position(Blob pattern, long start)
      throws SerialException, SQLException {
    isValid();
    return position(pattern.getBytes(1, (int) (pattern.length())), start);
  }

  /**
   * Writes the given array of bytes to the <code>BLOB</code> value that
   * this <code>Blob</code> object represents, starting at position
   * <code>pos</code>, and returns the number of bytes written.
   *
   * @param pos the position in the SQL <code>BLOB</code> value at which to start writing. The first
   * position is <code>1</code>; must not be less than <code>1</code> nor greater than the length of
   * this <code>SerialBlob</code> object.
   * @param bytes the array of bytes to be written to the <code>BLOB</code> value that this
   * <code>Blob</code> object represents
   * @return the number of bytes written
   * @throws SerialException if there is an error accessing the <code>BLOB</code> value; or if an
   * invalid position is set; if an invalid offset value is set; if {@code free} had previously been
   * called on this object
   * @throws SQLException if there is an error accessing the <code>BLOB</code> value from the
   * database
   * @see #getBytes
   */
  public int setBytes(long pos, byte[] bytes)
      throws SerialException, SQLException {
    return setBytes(pos, bytes, 0, bytes.length);
  }

  /**
   * Writes all or part of the given <code>byte</code> array to the
   * <code>BLOB</code> value that this <code>Blob</code> object represents
   * and returns the number of bytes written.
   * Writing starts at position <code>pos</code> in the <code>BLOB</code>
   * value; <i>len</i> bytes from the given byte array are written.
   *
   * @param pos the position in the <code>BLOB</code> object at which to start writing. The first
   * position is <code>1</code>; must not be less than <code>1</code> nor greater than the length of
   * this <code>SerialBlob</code> object.
   * @param bytes the array of bytes to be written to the <code>BLOB</code> value
   * @param offset the offset in the <code>byte</code> array at which to start reading the bytes.
   * The first offset position is <code>0</code>; must not be less than <code>0</code> nor greater
   * than the length of the <code>byte</code> array
   * @param length the number of bytes to be written to the <code>BLOB</code> value from the array
   * of bytes <i>bytes</i>.
   * @return the number of bytes written
   * @throws SerialException if there is an error accessing the <code>BLOB</code> value; if an
   * invalid position is set; if an invalid offset value is set; if number of bytes to be written is
   * greater than the <code>SerialBlob</code> length; or the combined values of the length and
   * offset is greater than the Blob buffer; if {@code free} had previously been called on this
   * object
   * @throws SQLException if there is an error accessing the <code>BLOB</code> value from the
   * database.
   * @see #getBytes
   */
  public int setBytes(long pos, byte[] bytes, int offset, int length)
      throws SerialException, SQLException {

    isValid();
    if (offset < 0 || offset > bytes.length) {
      throw new SerialException("Invalid offset in byte array set");
    }

    if (pos < 1 || pos > this.length()) {
      throw new SerialException("Invalid position in BLOB object set");
    }

    if ((long) (length) > origLen) {
      throw new SerialException("Buffer is not sufficient to hold the value");
    }

    if ((length + offset) > bytes.length) {
      throw new SerialException("Invalid OffSet. Cannot have combined offset " +
          "and length that is greater that the Blob buffer");
    }

    int i = 0;
    pos--; // correct to array indexing
    while (i < length || (offset + i + 1) < (bytes.length - offset)) {
      this.buf[(int) pos + i] = bytes[offset + i];
      i++;
    }
    return i;
  }

  /**
   * Retrieves a stream that can be used to write to the <code>BLOB</code>
   * value that this <code>Blob</code> object represents.  The stream begins
   * at position <code>pos</code>. This method forwards the
   * <code>setBinaryStream()</code> call to the underlying <code>Blob</code> in
   * the event that this <code>SerialBlob</code> object is instantiated with a
   * <code>Blob</code>. If this <code>SerialBlob</code> is instantiated with
   * a <code>byte</code> array, a <code>SerialException</code> is thrown.
   *
   * @param pos the position in the <code>BLOB</code> value at which to start writing
   * @return a <code>java.io.OutputStream</code> object to which data can be written
   * @throws SQLException if there is an error accessing the <code>BLOB</code> value
   * @throws SerialException if the SerialBlob in not instantiated with a <code>Blob</code> object
   * that supports <code>setBinaryStream()</code>; if {@code free} had previously been called on
   * this object
   * @see #getBinaryStream
   */
  public java.io.OutputStream setBinaryStream(long pos)
      throws SerialException, SQLException {

    isValid();
    if (this.blob != null) {
      return this.blob.setBinaryStream(pos);
    } else {
      throw new SerialException("Unsupported operation. SerialBlob cannot " +
          "return a writable binary stream, unless instantiated with a Blob object " +
          "that provides a setBinaryStream() implementation");
    }
  }

  /**
   * Truncates the <code>BLOB</code> value that this <code>Blob</code>
   * object represents to be <code>len</code> bytes in length.
   *
   * @param length the length, in bytes, to which the <code>BLOB</code> value that this
   * <code>Blob</code> object represents should be truncated
   * @throws SerialException if there is an error accessing the Blob value; or the length to
   * truncate is greater that the SerialBlob length; if {@code free} had previously been called on
   * this object
   */
  public void truncate(long length) throws SerialException {
    isValid();
    if (length > len) {
      throw new SerialException(
          "Length more than what can be truncated");
    } else if ((int) length == 0) {
      buf = new byte[0];
      len = length;
    } else {
      len = length;
      buf = this.getBytes(1, (int) len);
    }
  }


  /**
   * Returns an
   * <code>InputStream</code> object that contains a partial
   * {@code Blob} value, starting with the byte specified by pos, which is
   * length bytes in length.
   *
   * @param pos the offset to the first byte of the partial value to be retrieved. The first byte in
   * the {@code Blob} is at position 1
   * @param length the length in bytes of the partial value to be retrieved
   * @return <code>InputStream</code> through which the partial {@code Blob} value can be read.
   * @throws SQLException if pos is less than 1 or if pos is greater than the number of bytes in the
   * {@code Blob} or if pos + length is greater than the number of bytes in the {@code Blob}
   * @throws SerialException if the {@code free} method had been previously called on this object
   * @since 1.6
   */
  public InputStream getBinaryStream(long pos, long length) throws SQLException {
    isValid();
    if (pos < 1 || pos > this.length()) {
      throw new SerialException("Invalid position in BLOB object set");
    }
    if (length < 1 || length > len - pos + 1) {
      throw new SerialException(
          "length is < 1 or pos + length > total number of bytes");
    }
    return new ByteArrayInputStream(buf, (int) pos - 1, (int) length);
  }


  /**
   * This method frees the {@code SeriableBlob} object and releases the
   * resources that it holds. The object is invalid once the {@code free}
   * method is called. <p> If {@code free} is called multiple times, the
   * subsequent calls to {@code free} are treated as a no-op. </P>
   *
   * @throws SQLException if an error occurs releasing the Blob's resources
   * @since 1.6
   */
  public void free() throws SQLException {
    if (buf != null) {
      buf = null;
      if (blob != null) {
        blob.free();
      }
      blob = null;
    }
  }

  /**
   * Compares this SerialBlob to the specified object.  The result is {@code
   * true} if and only if the argument is not {@code null} and is a {@code
   * SerialBlob} object that represents the same sequence of bytes as this
   * object.
   *
   * @param obj The object to compare this {@code SerialBlob} against
   * @return {@code true} if the given object represents a {@code SerialBlob} equivalent to this
   * SerialBlob, {@code false} otherwise
   */
  public boolean equals(Object obj) {
    if (this == obj) {
      return true;
    }
    if (obj instanceof SerialBlob) {
      SerialBlob sb = (SerialBlob) obj;
      if (this.len == sb.len) {
        return Arrays.equals(buf, sb.buf);
      }
    }
    return false;
  }

  /**
   * Returns a hash code for this {@code SerialBlob}.
   *
   * @return a hash code value for this object.
   */
  public int hashCode() {
    return ((31 + Arrays.hashCode(buf)) * 31 + (int) len) * 31 + (int) origLen;
  }

  /**
   * Returns a clone of this {@code SerialBlob}. The copy will contain a
   * reference to a clone of the internal byte array, not a reference
   * to the original internal byte array of this {@code SerialBlob} object.
   * The underlying {@code Blob} object will be set to null.
   *
   * @return a clone of this SerialBlob
   */
  public Object clone() {
    try {
      SerialBlob sb = (SerialBlob) super.clone();
      sb.buf = (buf != null) ? Arrays.copyOf(buf, (int) len) : null;
      sb.blob = null;
      return sb;
    } catch (CloneNotSupportedException ex) {
      // this shouldn't happen, since we are Cloneable
      throw new InternalError();
    }
  }

  /**
   * readObject is called to restore the state of the SerialBlob from
   * a stream.
   */
  private void readObject(ObjectInputStream s)
      throws IOException, ClassNotFoundException {

    ObjectInputStream.GetField fields = s.readFields();
    byte[] tmp = (byte[]) fields.get("buf", null);
    if (tmp == null) {
      throw new InvalidObjectException("buf is null and should not be!");
    }
    buf = tmp.clone();
    len = fields.get("len", 0L);
    if (buf.length != len) {
      throw new InvalidObjectException("buf is not the expected size");
    }
    origLen = fields.get("origLen", 0L);
    blob = (Blob) fields.get("blob", null);
  }

  /**
   * writeObject is called to save the state of the SerialBlob
   * to a stream.
   */
  private void writeObject(ObjectOutputStream s)
      throws IOException, ClassNotFoundException {

    ObjectOutputStream.PutField fields = s.putFields();
    fields.put("buf", buf);
    fields.put("len", len);
    fields.put("origLen", origLen);
    // Note: this check to see if it is an instance of Serializable
    // is for backwards compatibiity
    fields.put("blob", blob instanceof Serializable ? blob : null);
    s.writeFields();
  }

  /**
   * Check to see if this object had previously had its {@code free} method
   * called
   */
  private void isValid() throws SerialException {
    if (buf == null) {
      throw new SerialException("Error: You cannot call a method on a " +
          "SerialBlob instance once free() has been called.");
    }
  }

  /**
   * The identifier that assists in the serialization of this
   * {@code SerialBlob} object.
   */
  static final long serialVersionUID = -8144641928112860441L;
}
